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A: Fachverband Atomphysik

A 21: Interaction with Strong or Short Laser Pulses II

A 21.4: Vortrag

Mittwoch, 4. März 2009, 17:30–17:45, VMP 6 HS-C

Electronic Wavepackets in Lithium — •Michael Schuricke, Jochen Steinmann, Ganjun Zhu, Manuel Kremer, Bettina Fischer, Robert Moshammer, Alexander Dorn, and Joachim Ullrich — Max Planck Institut für Kernphysik, Heidelberg, Germany

Whenever an excitation process coherently transfers population from an initial state to several final states a wavepacket is created. Its dynamics will be determined by the number of excited states, their energy differences and their spatial wavefunctions. The creation of a wavepacket can be achieved with a single photon or as in this case with several photons, as long as the final states lie within the coherence bandwidth of the laser pulse.
In our experiment a superposition of 4p and 4f states was excited by three-photon absorption from a Ti:Sa laser pulse with 800 nm wavelength and 20 fs duration. The peak intensity of the pulses was kept moderate and therefore the ionization rate for a single pulse was negligible. The evolution of the wave packet was probed by a variable delayed probe pulse ionizing the atoms and determining the momenta of the ejected electrons. As result, dramatic changes in the momentum distribution as a function of delay time were observed.
By shaping the spectral profile of the laser, it was also possible to excite superpositions of the 9p,f and 10p,f states via three photon excitation. The measurements allow to deduce the multiphoton excitation amplitudes and their relative phases with respect to the different intermediate states.